Oscillation generator



w; E. BOWER March 7, 1933.

OSCILLATION GENERATOR Filed April 15, 1950 INVENTOR.

MW, v BY ATTORNEY Patented Mar. 7, 1933 UNITED STATES WARD E. BOWEB, OF WASHINGTON, DISTRICT 01' COLUMBIA 'OSGILLATION Application filed April 15,

v My invention relates broadly'to oscillation generators and more particularly to a construction of oscillation generator capable of forming a secondary standard of frequency.

One of the objects of my invention is to provide an oscillation generator which may form a secondary standard of frequency and which may be readily transported for comparing various forms of oscillator circuits withthe primary frequency standard with a .high degree of accuracy.

Another object of my invention is to pro vide. a construction of a secondary standard of frequency which includes a piezoelectric 'crystaldevice which may be set into vibration by operation of a mechanical vibratory system for generating oscillations of constant frequency comparable with the frequency of the primary standard, the construction of the secondary standard being such that it is capableof transportation from place to place for reproducing oscillations of the desired j'frequency.

Still another object of my invention is to i provide an oscillation generator in which a mechanical system is operated under control of the generated oscillations for mechanically flexing a piezoelectric crystal element and producing thereby oscillations of constant freqency. y a

A still further object of my invention is to 'provide'a construction of secondary frequency standard in which a piezoelectric crystal element is mounted in relation to a mechanical vibratory system which maintains the piezoelectric crystal element in a state of mechanical flexure for the, generation, of electrical oscillations of constant frequency.

A further object of my invention is to provide an arrangement of piezoelectric crystal 'systeman'd mechanical vibrating system as- 's'ociated therewith by which the piezoelectric crystal may be subjected to compressional and rarefactional forces in step with the natural frequency thereof for generating constant frequency oscillations.

' Other and furtherobjects of my invention reside in the mechanical arrangement of driving system and piezoelectric generating systom as set forth more fully in the specificatio'n PATENT OFFICE companying drawing, in which:

Figure 1 is a diagrammatic view showing the circuit arrangement for the secondary frequency standard of my invention; and Fig. 2 illustrates a modified form of mounting for the piezoelectric crystal element employed in the secondary frequency standard of my invention.

The primary frequency standard is generally erected in alaboratory where provision may be made for the maintenance of an exact temperature with constant humidity condition in the vicinity of the frequencyfixing device. An elaborate system of temperature control is generally employed and other precautions are taken to carefully maintain constant conditions in the vicinity of the frequency fixing device. The primary fre- I quency standard is generally erected in the laboratory and is a permanent fixture therein. A secondary standard of frequency on the other hand is a portable apparatus which simulates as closely as possible the characteristics of'the primary frequency standard, the secondary frequency standard being readily transportable for the comparison of many diflerent forms of oscillator circuits with the frequency which is developed by the secondary standard of frequency.

My invention provides means for fixing the frequency of oscillations and maintaining the circuits associated with the apparatus in continuous oscillation. I provide a vibratory system which is operated in step with the oscillation circuit for mechanically flexing the piezoelectric crystal element which is connected in the oscillation circuit and establishing constant frequency, oscillations. f 4

Referring to the drawing in more detail I reference character 1 indicates a massive framework supported on base 4, the framework being constructed to withstandthe tension of a stretched magnetic wire 9 which extends between the extremity of the flat spring 2 and the laterally projecting supporting arm 3. The spring 2 is provided with a resilient bowed portion 6 thereon which adds to the resiliency thereof. The laterally pro- 1 jecting arm 3 is rigid and is provided with an insulated chuck member 10 which extends 'upwardly therethrough and engages the lower end of the magnetic wire 9, an adjusting screw device 11 being operated to move chuck 10 for imparting to the magnetic wire 9 the desired tension. 7 The piezoelectric crystal element 7 is supported upon the flat spring 2 insuch manner that flexing of the flat spring 2 imparts mechanical forces to the piezoelectric 'crystal element 7 An 'upper electrode 8 contacts with theltopsurface of the piezoelectric crystal element 7- and connects through lead 85" with the inputsystem of the thermionic tube/21. The thermionic tube 21 is coupled through transformer 23 with the input circuit of amplified tube 22. The output circuit of amplifier tube 22includes the ammeter 24, head telephones 25,,

and the magnet windings 16 and 17 which are wound upon theoppositely directed magnet poles l4 and 15. The pole pieces 14 and 15 arevcarried by a frame structure 12 which is adjustably positioned along the vertical standard 1 by means of the slidable collar 18 which fits around the standard 1 and is s'ecured in selected position; thereon by means of set screw 18%, .By the vertical adjustment of the magnets 14 and 15, I am able to selectively apply the magnetic forces to the magnetic wire member 9 for. setting the wire into a state of Vibration. In order to produce certainifrequencies of vibration of the magnetic wire 9, I provide an adjustable member 19 which projects laterally from the collar 28 which is vertically adjustablcalong standard 1 and which may be selectively set in position thereon by means of set screw 28a. The member 19 contacts with magnetic wire member 9 and vdetermines the position of a vibratory node along the magnetic wire 9.

If the member 19 engages the wire ,9 midway between the endsthereofthen'thefrequency of vibration will be twice the fundamental frequency of the wire 9. v A limited number of integral frequencies are obtainable by selectively positioning the magnetic system 14-15 and laterally'projecting member; 19 along the wire 9. The plate potential for the electron tubes constituting the oscillator and amplifier system is supplied from battery 26. The cathodes of the electron tubes are. heated from battery 27. j 1

.There are thus two separate mechanical vibrating elements which will have different individual natural frequencies, in the vibrating system on which the crystal is mounted,

' the spring 2 and the magnetic wire 91which are'meohanically coupled together, and this i v coupled vibrating system will have a plurality ofresonant frequencies and a broad response curve as contrasted with the narrow mechanical resonance peak of a single mechanical vibrating element.

7 r For purposes of scann ng in systems of television or picture. transmission, a small mirror 20 may be carried by the magnetic wire member 9 in such a position that a beam of light may be reflected over a given angular displacement. By reason-of the control which-is offered by the piezoelectric crystal element, the vibratory movement of the mirror 20 may be maintained at extremely constant amplitude.

In Figure 2, I have shown a modified form of mounting for the piezoelectric crystal element. In this arrangement the frame 1 is provided with an angular base mounting 36 and an upper horizontally extending portion 30 from which depends the piezoelectriccrystal element 29, The :free end of the piezoelectric crystal element 29 is coupled throughjaw member 31 with the Wire mem-c her 9 whereby vibrations developed along wire member'9 are imparted to the piezoelectric crystal element. 29' so'that a compressional and rarefactional force is ap plied toxthe piezoelectric crystal generating electrical oscillations which are suppliedto the electron tube circuits The piezoelectric voltage alternates between its maximum and minimum values in phase with the displacement of the magnetic wire 9; In Figure 1, the transverse vibrathrough leads 34 and 35 which connect to the electrodes 32 and '83 on the piezoelectric crystal element.

tions of the wire are sinusoidal. As these vibrations are applied to the piezoelectric crystal element, voltages generated thereby set whichare transferred to electron tube amplifier22 and amplified-thereby The electromagnetic windings 16 and 17 in operating upon magnetic subjecting the in mechanical flexure thus generating the oscillations of constantffrequency. In the oscillation generator which I have described, synchronized undulated currents are fed wire 9 continue the cycle of back in phase with the elastic displacement of the wire, and oscillations may be maintained throughout the entire audios frequencyrange, that is, from the lowest audible frequency up to 5000 cycles or more.

While I have described my invention in magneticwire held between said strip and a portion of said support, electromagnetic meansmounted upon said support for nperleli i piezoelectric crystal element asupport, a resilient strip a up oscillationsin the electron tube circuit 21 ating upon the wire and being adjustable in position upon the support along the length of said wire, a fret to engage said wire mounted upon said support and being adjustable upon the support to a desired point along the length of said wire whereby the resonant frequency of the oscillator is controlled, and an electron tube amplifier having its input connected to said crystal and its output connected to said electromagnetic means.

2. In a generator of oscillations of controlled frequency, a support, a piezoelectric crystal carried by said support, a tensioned magnetic Wire having one end connected to said crystal, electromagnetic means carried by said support for acting upon said wire to impart vibrations to the wire and crystal and being adjustable whereby the resonant frequency of the oscillator is controlled, and an electron tube amplifier having its input connected to said crystal and its output connected to said electromagnetic means.

WARD E. BOWER. 

